Posted By: fostertomIs that what the nukes are for then? For when renewables stop completely? Does that actually happen - windless winter North Sea -for how long?

Quite difficult to ramp up traditional Nuclear power. It is designed for baseload (and export in France's case). SMRs may be different (and UK has blown the headstart they had on that technology as usual). Gas Generators will be needed for the forseeable future; very flexible and can be wound up and down very quickly. However, you have to pay for them sitting idle (as you do for renewables).

It still seems short-sighted that no UK Government has put any serious cash into developing the UK's huge tidal resources.

They did put tidal (stream) into the last CfD auction and we got 11 projects generating 50MW, which is a £12million budget. I don't know if that counts as 'serious' cash in your books, but it's certainly helpful, and given that the CfD price was £198/MWh (i.e a lot more expensive than Hinkley, but significantly cheaper than the last round of tidal stream at £350 odd), that is demonstrating significant govt subsidy to help get this nascent tech to a point where it's cheap enough to compete. https://www.offshore-energy.biz/uk-supports-11-tidal-energy-projects-with-record-capacity-of-50mw-in-latest-cfd-scheme/

I was aware of Orbital Marine and SIMEC Atlantis ( and have invested in both companies in the past). But HydroWing and the Spanish Magallanes Renovables (and MOR Energy and Vdant Isles) are new to me. Magallanes ATIR boat with a massive turbine-pair on the bottom looks quite inconvenient to launch, or at least it needs a deep port. The one they've got has been running for 6 years it seems, so I guess it works. Hydrowings liftable wing is quite clever as it solves the servicing problem (at the cost of a special barge). It will be interesting to see who winds out of Orbital and Hydrowing on cost (I don't think the 'needs a 70-tonne crane to service' underwater designs are ever going to be cheap enough, BICBW).

@ djh:
Incomplete re your original question and you may have read this already?

https://www.nationalgrideso.com/electricity-explained/how-do-we-balance-grid/what-are-constraints-payments#:~:text=When%20there%20are%20physical%20constraints%20on%20the%20network,Generators%20are%20then%20compensated

Interesting electricity day today, the UK was generating more renewable power than we could consume.

Overnight, the strong winds meant we had the cheapest power in Europe, therefore we exported much of our excess wind power to our neighbours and curtailed the rest.

There is an emerging problem in Europe that PV owners are not reducing production as they theoretically should in response to low/negative prices (did anyone here switch off PV today?). PV is embedded, so difficult for the transmission operators to curtail.

Today, they paid other countries (including us) to absorb their excess PV by curtailing more of our wind. But we are all building more PV so that strategy might not work much longer.

For consumers, many of us had another free electricity day today on Agile and other variable tariffs. Only a couple of years ago, free electricity was noteworthy and only happened at weekends, but I've lost count how many free electricity days there have been this year (a dozen perhaps, anyone keeping count?).

Throughout all this, a small amount of gas and biomass power kept running, presumably paid by the grid to stay on for stability (as the electricity prices weren't covering their fuel bills).

Posted By: WillInAberdeenFor consumers, many of us had another free electricity day today on Agile and other variable tariffs.

We had a free electricity hour on Octopus - encouraged to use more than we would normally between 1-2pm. We turned everything on that we could (dishwasher, washing machine, induction hob, electric car charger) and the result was we used 3.75kWh instead of the typical 0.06kWh at this time of day. This amounted to a whopping 86p rebate.

I realise this is summer time and we may not be a typical household (although I'd argue those loads are fairly common), but I'm genuinely curious - how much of a problem is surplus power at the moment?

Is it just a financial problem due to price instability, or an actual physical problem as we have to put it 'somewhere'?

Could we be using it to power more pumped storage (like Dinorwig) or is that not 'useful' storage because it is instantaneous backup rather than base load?

Posted By: WillInAberdeenThere is an emerging problem in Europe that PV owners are not reducing production as they theoretically should in response to low/negative prices (did anyone here switch off PV today?). PV is embedded, so difficult for the transmission operators to curtail.

In this country AIUI PV isn't contracted to be curtailed because (a) history and (b) lots of small distributed generators. I don't know what the situation is in any other European countries.

But it seems to me that large solar farms could be curtailed just like wind farms. Output from domestic installations is constrained by law, so there's always the possibility of changing the law if required to prevent problems getting worse. So I don't see any fundamental problem, just the usual slow-moving legislatures. Am I wrong?

AIUI the issue in Germany is they have 90GWp of panels but the country only uses 50GW of power, so they swing from oversupply by day to undersupply at night, with big accompanying price swings, negative then pricey. They're building another 10GW of panels each year.

The solar (including the multi MW farms) is connected into the Distribution networks, not the Transmission networks, who are separate companies. The Transmission operator has to balance the grid but has no contract or relationship with the solar farms or with households. So they cannot enforce them to shut down on sunny days, they don't even know who's producing, or how much. Some windfarms are bigger (GW) so are connected to the Transmission system and can be curtailed.

On top of that, German PV owners get attractive historic FITs they don't want to turn off, and many don't even have smart meters, let alone smart inverters allowing remote control by the TNO.

We're only a few years behind, and our pricing is getting interconnected by HVDC. We have about 2GW of pumped storage to absorb oversupply, but it's much slower to build more of that than PV.
My understanding is secondhand from analysts over there, read back previous posts in blogs such as
https://gemenergyanalytics.substack.com/p/the-reasons-for-negative-prices
https://de.linkedin.com/posts/lionhirth_negative-preise-ungeregelte-solaranlagen-activity-7232716336383098880-0KcC



Oversupply is as serious a technical problem as undersupply, both will trigger blackouts for safety. In theory the market should solve this, by negative price incentives for suppliers to cease oversupply, but seems to be a bit difficult in practice.

In an effort to help, I had 12 hours free electricity yesterday and ran the tumble dryer and dehumidifier continuously on the clothes it was too rainy to hang out... Octopus also gave me a free takeaway coffee so it's not all bad!

Posted By: WillInAberdeenAIUI the issue in Germany is they have 90GWp of panels but the country only uses 50GW of power, so they swing from oversupply by day to undersupply at night, with big accompanying price swings, negative then pricey. They're building another 10GW of panels each year.

The obvious question is why? Why continue making their problem worse?

The Transmission operator has to balance the grid but has no contract or relationship with the solar farms or with households.

But they could have - it's just a matter of changing the law.

On top of that, German PV owners get attractive historic FITs they don't want to turn off, and many don't even have smart meters, let alone smart inverters allowing remote control by the TNO.

Are domestic systems causing oversupply or is it large solar farms?

Posted By: WillInAberdeenWhy continue building? They want to get to net zero all year round, not just in summer, so that will need a lot of panels (200 GW+ planned). Most of that production will need to be curtailed in summer. We are doing the same with wind and PV.

Wind tends to generate more in winter than summer, so it sounds like they should be prioritising wind and restricting solar.

Don't think you can just change a law to break up existing contracts between companies and impose new ones with different companies, politically or legally. What would a compulsory roll-out of remotely-controlled inverters look like?

Well no, that's not how politics works. You have to buy off vested interests, at least to the point that you carry a majority of votes. When you say 'remotely-controlled inverters' do you mean for solar farms or domestic? And for domestic do you mean for new installs or existing ones? The answers are obviously different for each case. Indeed there's likely different answers for existing and new solar farms, but there's just money involved there and not many votes. But basically the government can do what it wants if it really sets its mind to something when it comes to contracts.

Looks like we were importing from EU but exporting to Ireland, so our overall net import was 2GW at lunchtime 22 Aug. We were simultaneously curtailing 3.5GW of our own excess wind power.

This happens when EU imports are very negative price (so we are being paid to import by our neighbours, to help manage their excess). It's better economics for us to accept their excess power, even if we have to pay for curtailment of our own windfarms.

UK are planning to triple our PV and wind capacity in the next five years to 110GWp, vs our summer demand 25GW.

This is a really great problem to have! Brilliant news.

We should see batteries and electrolysis built, to store some excess, but a) we cant build them as fast as PV and b) their capital cost means they won't build just to run at summer lunchtimes. So we should still have excess power and zero/negative prices sometimes.

https://wind-curtailment-app-ahq7fucdyq-lz.a.run.app/

From here, it's a hobby website but seems ok.

Surely at least one other approach would be to add some more storage to the network, that was equipped to provide frequency stabilisation or whatever services are required? The storage could be batteries or hydro or whatever (hydrogen in underground caverns looks like a reasonable candidate in the UK).

Or require all domestic generators to fit supply interrupters that can be remotely controlled by some means less drastic than taking the mains supply out of spec. Or some subset of generators?

(haven't read the report yet, so maybe it answers this)

Edit: they were as apparently building a couple of GW scale pumped hydro projects in Queensland, but these are being abandoned due to huge budget overrun. Attention switching to grid batteries instead.

If it looks like being an issue then isn't the DNO the ultimate arbiter for grid tied installs.

To get paid for export you need to use and pay for a MCS installer or jump through a few hoops to get discretionary payments, if not MCS. I'd guess there's an awful lot of self installed/non MCS PV systems that aren't registered with a DNO.

When we applied to double our export a few years ago, our DNO had no record of the professionally installed MCS system installed in 2015! I hope their record keeping has improved!